It's really unlikely any will ever be genetically modified to not cause weight gain or hangovers

Genetically modified (GM) foods have caused widespread controversy ever since Californian company Calgene first started selling its Flavr Savr tomatoes in 1994. Two years later, the first GM seeds were permitted to be planted in the USA for commercial use. The debate has raged on from there.

The United States is the leader in genetically
modified food production, a dubious honor as it turns out. When polled,
slightly more than a third of Americans believed that GM foods are safe. 93%
insist the American federal government should require food labels to indicate
which foods have been genetically modified or bio-engineered. Currently 64
countries require GM labeling, 28 of them in the European Union. Such labeling
is voluntary in the USA and Canada. Critics of the voluntary approach point to
South Africa, where a study found that 31% of products sold and labeled as
GM-free actually contained more than 1% of GM materials. Above this
threshold, food producers were supposed to admit their products contained GM ingredients.

In 2013, 70.1m hectares of US farmland were dedicated to producing biotech crops, predominantly maize (corn), soybean, cotton, canola, sugar beet, alfalfa, papaya, and squash. Brazil came in at the #2 spot with 40.3m hectares, followed by Argentina (24.4m) and India (11.0m). 88% of corn and 94% of the soy grown in the USA is genetically modified. Recently, a GM cultivar for rice was approved in the USA.

If every beer conformed to the German Beer Purity Law of 1516, then the genetically modified discussion as it relates to beer would be a moot one. The Reinheitsgebot promulgated that only water, barley, and hops (and later yeast and wheat) could be used in the manufacture of beer. There have been over 450 field tests for GM wheat in Europe and the US, but no genetically modified wheat is presently available for commercial use. Barley remains a boutique crop, and the costs shoot up immensely with each additional characteristic added to the barley plant, so the economics may never be sound enough for commercially available GM barley plants.

The GM culprit in beer, for the moment, is corn and, to a lesser extent, soybeans. There are several varieties of Japanese happoshu which use soybeans instead of malted barley. Kirin and Asahi both manufacture these types of beers. And as soy is a major crop in the USA, it's not unforeseen for small amounts of soy to wind up in lots and lots of products, including beer.

Corn and its sickeningly sweet derivative, high fructose corn syrup, seem to find their way into everything processed. Corn, rice, and other fillers have long been a staple of American adjunct style lagers. Of the mainstream beer brands brewed in North America, Corona, Pabst Blue Ribbon, Budweiser, Guinness, Fosters, Coors, Red Stripe, and Michelob use either GM corn, GM corn syrup, GM sugars, and possibly GM rice. This is, by no means, an exhaustive list.

But what about American craft brewers? Could they be using GM ingredients, too? That depends who's behind the craft brewery. As a test, I e-mailed five American craft brewers (Ninkasi, Anderson Valley, Rogue, Deschutes, and Modern Times) to inquire if any incorporated genetically modified ingredients into their brews. All responded, and none said they did so knowingly. It must be noted that all five of these breweries are independently owned. Their reputation depends on them using the finest ingredients. If news got out that they were using GM fillers, their core customers would desert them.

But not all craft breweries are independent anymore. As a gambit to edge into the craft beer arena, mainstream GM-loving brewing powerhouses have started to buy up former independents. Blue Moon Brewing Company was founded as an independent in 1995 in Golden, Colorado. It's now an entity of Tenth and Blake Beer Company, the craft and import division of MillerCoors. The Brewers Association has already lambasted Blue Moon for not mentioning on the bottle that it is actually produced by MillerCoors, an omission that allows Blue Moon to continue to pretend to be the independent craft brewery it no longer is. A number of other once craft breweries have also been scooped up by the majors - Blue Point, Goose Island, 10 Barrel Brewing. Would anyone really be aghast that the recipes were slowly being adulterated with GM ingredients to cut costs, especially when U.S. labeling laws are so lax?

Even outside the USA, just because a beer doesn't state on the label that it contains GM ingredients doesn't mean it's really GM free. Take South Korea and Japan, two of the 64 countries making GM food labeling mandatory. Every quarter Japan requires 2.7m tons of corn for livestock feed and another 1m tons for food, sweeteners, and other uses, like an adjunct in beer. While the yen remained strong, Japan purchased 70% of its corn from US sources - statistically, these would be mostly or all GM ones. After the yen declined, Japan made up the shortfall from Brazil, Argentina, and Ukraine, the first two countries already well known for GM corn.

South Korea imports 10.2m metric tons of corn annually, 80% of that for animal feed, the other 20% for "other uses." Korea is a sophisticated market and quickly shifts suppliers dependent on price, so some years Korea could use up to 98% of imported U.S. corn and other years as low as 2%. Mainstream South Korean brewers, famous for producing some of the worst lagers in Asia, readily admit to using rice and corn to generate a mild taste, quite possibly genetically modified.

So, in the end, it is irrelevant whether a country requires labeling or not if that country imports GM inputs. If a brewery is organic and/or an independent, there is more than a fair chance, wherever it's located, that it's GM free. The taint of fillers, additives, or GM ingredients can sink a small brewery's ship. To be absolutely sure a beer remains free of GM ingredients, should you care, e-mail the brewery itself. A vaguely worded response with lots of buzzwords or no response at all translates into "We knowingly use GM's."